HR: 0800h
AN: U11A-0810    [Abstracts]
TI: Chasing Earthquakes at Focal Depth: Personal Perspective From 3.6 km Depth
AU: Diament, M
EM: diament@ipgp.jussieu.fr
AF: Institut de Physique du Globe de Paris, case 89, 4 place Jussieu, Paris, 75252 France, Metropolitan
AU: * Panet, I
EM: panet@ipgp.jussieu.fr
AF: Institut de Physique du Globe de Paris, case 89, 4 place Jussieu, Paris, 75252 France, Metropolitan
AU: * Panet, I
EM: panet@ipgp.jussieu.fr
AF: Laboratoire de Recherche en Géodésie, Institut Géographique National, 6/8, avenue Blaise Pascal, ENSG, Champs sur Marne, Marne la Vallée, 77455 France, Metropolitan
AU: Mikhailov, V
EM: mikh@ifz.ru
AF: Institute of Physics of the Earth, Russian Academy of Sciences, B. Gruzinskaya 10, Moscow, 123995 Russian Federation
AU: Tikhostky, S
EM: sat@ifz.ru
AF: Institute of Physics of the Earth, Russian Academy of Sciences, B. Gruzinskaya 10, Moscow, 123995 Russian Federation
AB: The launch of the space gravity mission GRACE in 2002 opens the way to the global monitoring of temporal variations of the gravity field. Because of their global coverage, the new space gravity data are of primary interest for characterizing earthquakes in areas less covered by geophysical or geodetical networks, such as the oceanic subduction zones. However, performant techniques are required in order to extract information from the space gravity data. We developed a statistical signal recognition technique to identify signals caused by displacement of unknown magnitude on fault planes of given position and dimension. We showed that gravity field variations caused by large earthquakes such as the Alaska 1964 or Chili-1960 could be recognized in GRACE data at the present-day GRACE accuracy level (Mikhailov et al, 2004). We then improved our method by taking into account the gravity effect of the superficial fluid envelops (atmosphere, oceans, hydrology ...) and by introducing wavelets to increase the signal to noise ratio in localized tectonic areas. We apply this improved method to the case of the December 26th, 2004 Sumatra-Andaman earthquake. Vertical displacements were obtained using edge dislocation in an elastic media. Comparison of the gravity signal with accuracy of the current GRACE models showed that the gravity signal associated with the earthquake can not be recognized visually, but can be extracted using our method. We also compared different fault plane models for the earthquake and conclude that discrimination between them is possible using space gravity data.
DE: 1217 Time variable gravity (7223, 7230)
DE: 1242 Seismic cycle related deformations (6924, 7209, 7223, 7230)
DE: 3280 Wavelet transform (3255, 4455)
SC: Union [U]
MN: Fall Meeting 2005